Ok we had a 2003 dodge ram 3500 brought to our shop the other day for a no start issue...Well when cranking we were only getting aorund 1200 pounds to the rail..The dealership wouldnt give us the specs. so the tech working on it had to call his connection in cummins. The guy said it should be around 35-3600 pounds while cranking...So we threw a cp3 in and still same issue,but we could get it started and it will drive down the road the fine and idle fine with a LIL spray of either.. ( yes I know NEVER USE IT )..Now not that many cummins come into our shop..mainly fords, so I curious on what you guys think it might be...thanks

 

Did you check the transfer pump to see if it was working, if the lift pump isn't working it will idle rough and lose power if you get on it as it's starving the CP3, and if you opened the system you removed the siphon and the CP3 won't prime .

 

I would start with Herb's recommendations first as it is easy to do. Next, did you change out the FCA (little black doohickey on the back of the CP3) when you changed the CP3 out? This is called the fuel control acuator and it controls the output of the CP3. The next thing to check is the return. There is a rail pressure relief valve located at the end of the common rail. It can become faulty or etched and leak fuel by and it goes into the return back to the tank and cause low pressure on the rail. It is a replaceable part for around $300 but you can also just cap it to see if it helps your problem before spending the money.

 

thanks for the input..yes the lift pump is working..When we crack the fuel filter we get fuel coming out of the housing...also how would you actually " cap " the relief valve?

 

A word of caution, your LP may look like it is working but honestly to prove that it is you should check the voltage drop across it. Funny things happen to fluids in vaccums.

 

You can use this Cummins Fuel Rail Plug / Cap - JD's Diesel Performance on a quick google search or you can just thread your stock banjo and put a pipe plug on it. I would go with this one you can buy, it looks much easier. This would be after you made sure the FCA was changed out with your CP3 though.

 

Seeing that's it's an '03, I'd be looking at the injectors first. There have been a lot of '03's in the forums lately with a "no start" thing going on. Winds up being the injectors. Check your batteries also.

 

ok ill look into that..as for the injectors we unplugged each one ( one at a time of course ), and everything seemed normal ( as in motor would act weird ). but we will have to check into that voltage drop across it... the tech said the guy at cummins said it could be a issue with the injector harness so we are popping off the valve cover now to see if it is messed up..will keep you updated..but please chime in if you have any other suggestions...and as for that sensor..when we plugged our scanner into the truck ( solaris ) it seemed to be working fine...

 

Forgot about the injector harness. It gets frayed as it goes under the aluminum housing of the valve cover. Also, low batteries like said above can also cause issues. All good suggestions. Good luck.

 

You know, if we are talking about a stock 2003 do you know if it has ever been flashed? The 2003 Dodge has if memory serves some 40 different ECM programs that again based on experience and memory can cause all sorts of issue all the whilst not throwing a code.

It has therefore also been my experience that the only way this can be solved reasonably is to get a smarty box and overwrite the ECM with their stock program. This program, for whatever reason, is 99+% trouble free and does in many cases cure these sorts of mystery issues.

Sure there is a cost associated to it but there is a line one needs to draw with respect to the number of hours you care to work on it as well.

Just an idea.